Stabilizing Highly Active Metastable Bi (101) Facet via Covalent Organic Frameworks to Break Activity-Stability...

Electrochemical CO₂ reduction reaction (eCO₂RR) offers a sustainable route to convert greenhouse gases into value-added chemicals. Bismuth (Bi) has emerged as a promising electrocatalyst for CO₂-to-HCOOH conversion due to its low cost, nontoxicity, and favorable adsorption properties for the key *OCHO intermediate. However, its relatively contracted 5d and expanded 6p orbitals lead to inevitable thermodynamically driven structural reconstruction during eCO₂RR, resulting in a persistent trade-off between activity and stability. Here, by tuning the balance between the electrochemical and thermodynamic steady states of layered Bi species leveraging interlayer interactions and spatial confinement provided by a two-dimensional covalent organic framework (COF), we achieve the selective exposure and stable maintenance of the highly active, metastable Bi (101) facet during eCO₂RR for the first time. The resulting catalyst achieves top-tier performance with 98.7 ± 0.1% HCOOH selectivity, exceptional stability over 230 h, and a flow cell HCOOH partial current density exceeding 350 mA cm^-2 at -1.0 V versus RHE, ranking it among the most efficient and stable electrocatalysts reported to date.